MARINE CORPS BASE QUANTICO, Va. — The Marine Corps announced Friday it will send 10 V-22 Ospreys to Iraq this year in the first combat mission for the hybrid aircraft expected to carry troops in and out of battle at unprecedented speed.

Built by Boeing Co. and Bell, a unit of Textron Inc., the planes' deployment marks a significant reversal for an aircraft program that was nearly scrapped after two deadly test crashes and a history of mechanical failures.

The medium-size, tilt-rotor plane — which takes off vertically like a helicopter and flies likes a plane — replaces the CH-46 Sea Knight, a 39-year-old assault helicopter used in the Vietnam War.

Demonstrated to reporters at Quantico Marine Corps Base, Va., on Friday, the Osprey can travel twice as fast and three times farther than the Sea Knight. The planes, equipped with radar, lasers and a missile defense system, each carry 24 combat-ready Marines and will accompany attack helicopters in Iraq, which come under gunfire and mortar attacks.

The Marines expect speed to protect the Osprey from the ground-fire Iraqi insurgents have used to down U.S. helicopters this year.

"The V-22 will be able to fly above the threat," said Lt. Gen. Castellaw, deputy commandant for Marine Aviation. "It's harder to shoot a rabbit that's running than one that is sitting still. We're talking about the ability to climb altitude outside of the heart of the threat over there."

'Most capable, survivable aircraft'"It is our fervent feeling that this aircraft is the most capable, survivable aircraft that we carry our most important weapons system in, which is the Marine or rifleman," he added.

Gen. James Conway, the commandant of the Marine Corps, said 171 Marines will accompany the Osprey set for September deployment to Al-Asad Airfield, the second largest air base in Iraq located 100 miles west of Baghdad.

"This is a great day for our corps," Conway said. "This deployment directly supports our corps' number one priority — the Marines and sailors in contact at the tip of the spear."

Like the Black Hawk used by the Army, the Marine Corps' Osprey strikes a dramatic, even intimidating form as it roars over the horizon. Landing in a clearing of trees at Quantico on Friday, gusts from two Ospreys sent dirt and blades of grass flying as far as 100 yards.

Castellaw rejected concerns that the Osprey might not be safe, emphasizing that it had been extensively tested and was fully operational.

In April 2000, 19 Marines died when their V-22 crashed in Marana, north of Tucson, Ariz. The accident was blamed partly on human error and mechanical problems.

Then in December 2000, four more Marines died in a crash in North Carolina due to a hydraulic malfunction.

Out of small arms range in secondsIn the demonstration flight at Quantico, the aircraft was off the ground and out of small-arms range in less than a minute. Once airborne, its rotors shifted from helicopter to airplane position in 12 seconds, and the transition was so smooth that passengers unprepared for the Osprey's next flight mode were jolted toward the back of the aircraft.

It can move from 110 knots to more than 200 knots as the aircraft shifts into airplane flight, said Lt. Col. Paul Rock, commander of the squadron headed to Iraq. It can hit speeds of nearly 350 knots, or more than 400 miles per hour.

Critics have raised questions about the maneuverability of the aircraft in some circumstances.

Pilots will face the same restrictions in the Osprey as they do in other helicopters and tactical adjustments will be implemented to avoid the risk, Castellaw said.

For example, Osprey pilots when in helicopter mode will have to avoid descending at a low air speed and high rate of descent, just as pilots of traditional helicopters.

"You don't want to do that in a helicopter, and you do not want to do that in a tilt-rotor," Castellaw said.

He said the Osprey has systems on board to warn pilots when they are descending from a high altitude with too much power in helicopter mode.